From: Marcos Paulo de Souza <mpdesouza@suse.de>
To: Joe Lawrence <joe.lawrence@redhat.com>
Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kbuild@vger.kernel.org,
Josh Poimboeuf <jpoimboe@kernel.org>,
Miroslav Benes <mbenes@suse.cz>, Petr Mladek <pmladek@suse.com>,
Marcos Paulo de Souza <mpdesouza@suse.com>
Subject: Re: [PATCH v7 04/10] livepatch: Add sample livepatch module
Date: Tue, 14 Mar 2023 15:17:13 -0300 [thread overview]
Message-ID: <20230314181713.tgpc7t7yia5nlhil@daedalus> (raw)
In-Reply-To: <20230306140824.3858543-5-joe.lawrence@redhat.com>
On Mon, Mar 06, 2023 at 09:08:18AM -0500, Joe Lawrence wrote:
> Add a new livepatch sample in samples/livepatch/ to make use of symbols
> that must be post-processed to enable load-time relocation resolution.
> As the new sample is to be used as an example, it is annotated with
> KLP_MODULE_RELOC and with KLP_SYMPOS macros.
>
> The livepatch sample updates the function cmdline_proc_show to print the
> string referenced by the symbol saved_command_line appended by the
> string "livepatch=1".
>
> Update livepatch-sample.c to remove livepatch MODULE_INFO statement.
LGTM:
Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Joao Moreira <jmoreira@suse.de>
> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
> ---
> samples/livepatch/Makefile | 1 +
> .../livepatch/livepatch-annotated-sample.c | 93 +++++++++++++++++++
> 2 files changed, 94 insertions(+)
> create mode 100644 samples/livepatch/livepatch-annotated-sample.c
>
> diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile
> index 9f853eeb6140..f2b41f4d6c16 100644
> --- a/samples/livepatch/Makefile
> +++ b/samples/livepatch/Makefile
> @@ -6,3 +6,4 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o
> obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o
> obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o
> obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o
> +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o
> diff --git a/samples/livepatch/livepatch-annotated-sample.c b/samples/livepatch/livepatch-annotated-sample.c
> new file mode 100644
> index 000000000000..4fe0e16423c7
> --- /dev/null
> +++ b/samples/livepatch/livepatch-annotated-sample.c
> @@ -0,0 +1,93 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
> + */
> +
> +/*
> + * livepatch-annotated-sample.c - Kernel Live Patching Sample Module
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/livepatch.h>
> +
> +/*
> + * This (dumb) live patch overrides the function that prints the
> + * kernel boot cmdline when /proc/cmdline is read.
> + *
> + * This livepatch uses the symbol saved_command_line whose relocation
> + * must be resolved during load time. To enable that, this module
> + * must be post-processed by a tool called klp-convert, which embeds
> + * information to be used by the loader to solve the relocation.
> + *
> + * The module is annotated with KLP_MODULE_RELOC/KLP_SYMPOS macros.
> + * These annotations are used by klp-convert to infer that the symbol
> + * saved_command_line is in the object vmlinux.
> + *
> + * As saved_command_line has no other homonimous symbol across
> + * kernel objects, this annotation is not a requirement, and can be
> + * suppressed with no harm to klp-convert. Yet, it is kept here as an
> + * example on how to annotate livepatch modules that contain symbols
> + * whose names are used in more than one kernel object.
> + *
> + * Example:
> + *
> + * $ cat /proc/cmdline
> + * <your cmdline>
> + *
> + * $ insmod livepatch-sample.ko
> + * $ cat /proc/cmdline
> + * <your cmdline> livepatch=1
> + *
> + * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
> + * $ cat /proc/cmdline
> + * <your cmdline>
> + */
> +
> +extern char *saved_command_line;
> +
> +#include <linux/seq_file.h>
> +static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
> +{
> + seq_printf(m, "%s livepatch=1\n", saved_command_line);
> + return 0;
> +}
> +
> +KLP_MODULE_RELOC(vmlinux) vmlinux_relocs[] = {
> + KLP_SYMPOS(saved_command_line, 0)
> +};
> +
> +static struct klp_func funcs[] = {
> + {
> + .old_name = "cmdline_proc_show",
> + .new_func = livepatch_cmdline_proc_show,
> + }, { }
> +};
> +
> +static struct klp_object objs[] = {
> + {
> + /* name being NULL means vmlinux */
> + .funcs = funcs,
> + }, { }
> +};
> +
> +static struct klp_patch patch = {
> + .mod = THIS_MODULE,
> + .objs = objs,
> +};
> +
> +static int livepatch_init(void)
> +{
> + return klp_enable_patch(&patch);
> +}
> +
> +static void livepatch_exit(void)
> +{
> +}
> +
> +module_init(livepatch_init);
> +module_exit(livepatch_exit);
> +MODULE_LICENSE("GPL");
> +MODULE_INFO(livepatch, "Y");
> --
> 2.39.2
>
next prev parent reply other threads:[~2023-03-14 18:17 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 14:08 [PATCH v7 00/10] livepatch: klp-convert tool Joe Lawrence
2023-03-06 14:08 ` [PATCH v7 01/10] livepatch: Create and include UAPI headers Joe Lawrence
2023-03-07 11:41 ` Marcos Paulo de Souza
2023-03-06 14:08 ` [PATCH v7 02/10] livepatch: Add klp-convert tool Joe Lawrence
2023-03-14 18:26 ` Marcos Paulo de Souza
2023-03-17 20:06 ` Joe Lawrence
2023-03-20 19:53 ` Marcos Paulo de Souza
2023-03-06 14:08 ` [PATCH v7 03/10] kbuild/modpost: create symbols.klp and integrate klp-convert Joe Lawrence
2023-03-14 18:48 ` Marcos Paulo de Souza
2023-03-06 14:08 ` [PATCH v7 04/10] livepatch: Add sample livepatch module Joe Lawrence
2023-03-14 18:17 ` Marcos Paulo de Souza [this message]
2023-03-06 14:08 ` [PATCH v7 05/10] documentation: Update on livepatch elf format Joe Lawrence
2023-03-07 11:48 ` Marcos Paulo de Souza
2023-03-06 14:08 ` [PATCH v7 06/10] livepatch/selftests: add klp-convert Joe Lawrence
2023-03-14 20:22 ` Marcos Paulo de Souza
2023-03-06 14:08 ` [PATCH v7 07/10] livepatch/selftests: test multiple sections Joe Lawrence
2023-03-06 14:08 ` [PATCH v7 08/10] livepatch/selftests: add __asm__ symbol renaming examples Joe Lawrence
2023-03-06 14:08 ` [PATCH v7 09/10] livepatch/selftests: add data relocations test Joe Lawrence
2023-03-06 14:08 ` [PATCH v7 10/10] livepatch/selftests: add static keys test Joe Lawrence
2023-03-14 20:23 ` [PATCH v7 00/10] livepatch: klp-convert tool Marcos Paulo de Souza
2023-03-17 20:29 ` Joe Lawrence
2023-03-17 23:20 ` Josh Poimboeuf
2023-03-20 19:23 ` Joe Lawrence
2023-04-11 10:06 ` Nicolai Stange
2023-05-02 23:38 ` Marcos Paulo de Souza
2023-05-03 19:54 ` Joe Lawrence
2023-05-09 20:34 ` Marcos Paulo de Souza
2023-03-20 20:15 ` Marcos Paulo de Souza
2023-04-19 20:27 ` Marcos Paulo de Souza
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